Deitze Otaduy - Academia.edu (original) (raw)
Papers by Deitze Otaduy
Analytica Chimica Acta, 2011
This paper describes the calibration process of a Visible-Near Infrared sensor for the condition ... more This paper describes the calibration process of a Visible-Near Infrared sensor for the condition monitoring of a gas engine's lubricating oil correlating transmittance oil spectra with the degradation of a gas engine's oil via a regression model. Chemometric techniques were applied to determine different parameters: Base Number (BN), Acid Number (AN), insolubles in pentane and viscosity at 40 • C. A Visible-Near Infrared (400-1100 nm) sensor developed in Tekniker research center was used to obtain the spectra of artificial and real gas engine oils. In order to improve sensor's data, different preprocessing methods such as smoothing by Saviztky-Golay, moving average with Multivariate Scatter Correction or Standard Normal Variate to eliminate the scatter effect were applied. A combination of these preprocessing methods was applied to each parameter. The regression models were developed by Partial Least Squares Regression (PLSR). In the end, it was shown that only some models were valid, fulfilling a set of quality requirements. The paper shows which models achieved the established validation requirements and which preprocessing methods perform better. A discussion follows regarding the potential improvement in the robustness of the models.
Laser Sources and Applications, 2012
Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used ... more Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used in different industrial applications sectors such as automobile, microfluidic, electronic and biomedicine. This technique offers several advantages over conventional methods, especially when a local deposition of energy and minimum thermal distortions are required. In LTW one of the polymeric materials needs to be transparent to the laser wavelength and the second part needs to be designed to be absorbed in IR spectrum. This report presents a study of laser weldability of ABS (acrylonitrile/butadiene/styrene) filled with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). These additives are used as infrared absorbing components in the laser welding process, affecting the thermal and optical properties of the material and, hence, the final quality of the weld seam. A tailored laser system has been designed to obtain high quality weld seams with widths between 0.4 and 1.0mm. It consists of two diode laser bars (50W per bar) coupled into an optical fiber using a non-imaging solution: equalization of the beam quality factor (M 2) in the slow and fast axes by a pair of micro step-mirrors. The beam quality factor has been analyzed at different laser powers with the aim to guarantee a coupling efficiency to the multimode optical fiber. The power scaling is carried out by means of multiplexing polarization technique. The analysis of energy balance and beam quality is performed in two linked steps: first by means ray tracing simulations (ZEMAX ®) and second, by validation. Quality of the weld seams is analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. The optimum laser power range for three different welding speeds is determinate meanwhile the clamping pressure is held constant. Additionally, the corresponding mechanical shear tests were carried out to analyze the mechanical properties of the weld seams. This work provides a detailed study concerning the effect of the material microstructure and laser beam quality on the final weld formation and surface integrity.
Agente: No consta 54 Título: Método de predicción lineal óptima para la reconstrucción de la imag... more Agente: No consta 54 Título: Método de predicción lineal óptima para la reconstrucción de la imagen en cámaras digitales con sensor de mosaico. Aviso: Se puede realizar consulta prevista por el art. 37.3.8 LP.
Electro-Optical and Infrared Systems: Technology and Applications, 2004
Despite MTF is widely accepted as the most complete figure of merit describing optical quality of... more Despite MTF is widely accepted as the most complete figure of merit describing optical quality of image intensifier tubes(IIs), it is not well-established neither in industrial nor governmental testing laboratories. This work aims to advance in the standardization of MTF testing procedures for modern IIs. A versatile device to measure MTF of IIs, based on different FFT related methods, was
Optical Sensing and Detection, 2010
ABSTRACT Marine engine oils are used for years without an oil change. During this long period of ... more ABSTRACT Marine engine oils are used for years without an oil change. During this long period of time the oil gets contaminated, not only by water and fuel but also by solid contaminants due to oxidation of the base oil, overreacted additives soot and other products of Heavy Fuel Oil combustion. This paper shows the design, development and assembly of a visible-near infrared (400-1100 nm) sensor that monitors several characteristics corresponding to in-use marine engine oil condition. Also, chemometric techniques (PLS) are applied for determining TBN, %insoluble in pentane, soot and water from visible-near infrared spectra, having in mind the low resolution capability of the extracted on-line sensor signal. Different prediction models for each oil parameter were obtained. These prediction models were developed by partial least squares regression from the VIS/NIR spectra. Finally, the sensor has been tested at low-speed crosshead engine (two stroke engine). So that, reference values for TBN, %insoluble in pentane, soot and water were obtained in the laboratory for every sample. During the validation test, the models showed: a) a correlation higher than or equal to 0.85; b) the slope for the regression model tends to one; c) low bias; and d) the root mean square error of prediction (RMSEP) and the standard error of performance (SEP) were similar and close to the laboratory's estimated error.
Optical Sensing and Detection, 2010
The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and indust... more The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with
IEEE International Conference on Image Processing 2005, 2005
We present an efficient Linear Minimum Mean Square Error (LMMSE) method for reconstructing full c... more We present an efficient Linear Minimum Mean Square Error (LMMSE) method for reconstructing full color images from single sensor Color Filter Array (CFA) data. We use a representative set of full color images to estimate the joint spatial-chromatic covariance among pixel color components. Then, we derive from it a set of joint color-space, small linear kernels which predict the missing color samples as linear combinations of their neighbor observed samples. The color arrangement of the local mosaic varies with the window's location, and this results into a different predictor for every local mosaic and color sample. As an extension, we include blur and noise in the training process, obtaining localized mosaic-constrained Wiener estimators that partially compensate for these degradations. We show that this simple method provides an excellent trade-off between performance and computational cost.
Electro-Optical and Infrared Systems: Technology and Applications II, 2005
The most straightforward way to describe the performance of an image intensifier tube, especially... more The most straightforward way to describe the performance of an image intensifier tube, especially under adverse conditions, is to predict the image it yields. In this work we have developed two different methods to provide realistic simulated images in low light level conditions: 1) Approximate Physical Model. A classical approach based on the simulation of the different degradation sources. It provides a good understanding of the image formation process. 2) Synthesis-by-analysis of real images. The observed noise is modelled through texture analysis tools and the image blur through the MTF. The resulting simulated images for both methods were compared with real intensified images (laboratory chart sights and natural images) taken under controlled conditions, close to the performance limits of an image intensifier tube. Both methods generated good results in terms of visual comparison for different object sizes, contrasts or luminances. These methods can be used as a new tool to predict the performance thresholds of the image intensifier. Only well-known or measurable parameters were used as input for the methods.
Electro-Optical Remote Sensing, 2005
In this paper, a decision support system for ship identification is presented. The system receive... more In this paper, a decision support system for ship identification is presented. The system receives as input a silhouette of the vessel to be identified, previously extracted from a side view of the object. This view could have been acquired with imaging sensors operating at different spectral ranges (CCD, FLIR, image intensifier). The input silhouette is preprocessed and compared to those stored in a database, retrieving a small number of potential matches ranked by their similarity to the target silhouette. This set of potential matches is presented to the system operator, who makes the final ship identification. This system makes use of an evolved version of the Curvature Scale Space (CSS) representation. In the proposed approach, it is curvature extrema, instead of zero crossings, that are tracked during silhouette evolution, hence improving robustness and enabling to cope successfully with cases where the standard CCS representation is found to be unstable. Also, the use of local curvature was replaced with the more robust concept of lobe concavity, with significant additional gains in performance. Experimental results on actual operational imagery prove the excellent performance and robustness of the developed method.
Procedia Engineering, 2012
ABSTRACT
Optik - International Journal for Light and Electron Optics, 2014
An efficient flat-top illuminating optical system optimized for an extended light source is prese... more An efficient flat-top illuminating optical system optimized for an extended light source is presented. The source is a high-brightness high divergence light emitting diode (LED), sized 1 mm × 1 mm, producing monochromatic emission (525 ± 5 nm) with viewing angle of 130 •. The design is based on a rotationally symmetrical catadioptric system, developed on a geometrical optics basis, and modelled with ZEMAX ® software. The device consists of two optical systems: (i) a collimating system which, in turn, is formed by an aspheric lenses system (low numerical apertures, NA < 0.26) and two-mirror system (0.26 < NA < 0.86), and (ii) an external mirror (NA > 0.86) designed and optimized for each purpose. By itself, the collimating system works with a residual divergence of  C = 1.46 •. The external mirror can be adequately designed to produce some given conditions. For instance, a flat-top profile is obtained in the selected focusing plane, with a maximum transversal intensity variation of 2.5% over 18 mm. In addition, when the focusing mirror is allowed to move along the optical axis in a ±1 mm range, other interesting profiles can be reached for a given working distance, therefore increasing the versatility of the system.
Optical Engineering, 2012
Laser transmission welding (LTW) of thermoplastics is a direct bonding technique already used in ... more Laser transmission welding (LTW) of thermoplastics is a direct bonding technique already used in different industrial applications sectors such as automobiles, microfluidics, electronics, and biomedicine. LTW evolves localized heating at the interface of two pieces of plastic to be joined. One of the plastic pieces needs to be optically transparent to the laser radiation whereas the other part has to be absorbent, being that the radiation produced by high power diode lasers is a good alternative for this process. As consequence, a tailored laser system has been designed and developed to obtain high quality weld seams with weld widths between 0.7 and 1.4 mm. The developed laser system consists of two diode laser bars (50 W per bar) coupled into an optical fiber using a nonimaging solution: equalization of the beam parameter product (BPP) in the slow and fast axes by a pair of step-mirrors. The power scaling was carried out by means of a multiplexing polarization technique. The analysis of energy balance and beam quality was performed considering ray tracing simulation (ZEMAX®) and experimental validation. The welding experiments were conducted on acrylonitrile/butadiene/styrene (ABS), a thermoplastic frequently used in automotive, electronics and aircraft applications, doped with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). Quality of the weld seams on ABS was analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. Mechanical properties of weld seams were analyzed by mechanical shear tests. High quality weld seams were produced in ABS, revealing the potential of the laser developed in this work for a wide range of plastic welding applications.
Microelectronic Engineering, 2014
In the present work thermal nanoimprint lithography of various commercial thermoplastic resists a... more In the present work thermal nanoimprint lithography of various commercial thermoplastic resists as matrixes for perylenediimides (PDIs) has been studied. This fabrication method reduced the number of fabrication steps, and therefore, the cost of the obtained distributed feedback (DFB) lasers. The optical properties of these devices are analyzed, aiming to optimize their performance.
Journal of Applied Physics, 2012
We report on the preparation and characterization, under optical pump, of second-order onedimensi... more We report on the preparation and characterization, under optical pump, of second-order onedimensional distributed feedback (DFB) lasers based on polystyrene films doped with a perylenediimide derivative, as active media. The DFB gratings were engraved on the substrates (SiO 2) by thermal nanoimprint lithography, followed by reactive ion etching. Laser emission wavelength was tuned from 554 to 583 nm by changing film thickness (h) between 240 and 1200 nm. The effect on the performance (emission wavelength, threshold, slope efficiency, number of modes, and spectral shape) of varying the grating depth (d) from 30 to 240 nm, for the whole range of h values, has been investigated. Although there is extensive work in the literature aiming to tune the emission wavelength of organic DFB lasers by h variation, the effect of changing d systematically has not been previously studied. Experimental results have been interpreted by models that take into account the presence of the grating by averaging either h or the effective refractive index. Single-mode emission (k 0) was observed for h < 1000 nm, while for thicker films lasing appeared at two different wavelengths (k 0 and k 1). Models indicate that k 0 and k 1 correspond to the TE 0 and TE 1 waveguide modes, respectively. It was found that d plays an important role in determining the DFB thresholds and slope efficiencies for two h regimes: (i) For h < 350 nm, lowest thresholds and highest slopes efficiencies were obtained with the shallower gratings; and (ii) for h > 1000 nm, d affects significantly the losses associated with the TE 1 mode, so single mode emission was achieved at k 0 or at k 1 for deep and shallow gratings, respectively. Finally, the shape of the emission spectra, both below and above threshold, has also been analyzed in order to clarify the physical mechanisms responsible for the existence of gain. Bragg dips were observed in the spectra below threshold only for devices with d/h larger than around 0.3 and their width increased with increasing d/h. In these cases, single-mode DFB emission appeared at the long-wavelength edge of the Bragg dip, indicating that index-coupling modulation contributes significantly to the gain process. On the other hand, for smaller d/h values, Bragg dips became too small to be detected, so gain coupling becomes the dominant mechanism accounting for the presence of gain.
Food Chemistry, 2012
This paper describes the calibration, validation and testing process of a low-cost on-line visibl... more This paper describes the calibration, validation and testing process of a low-cost on-line visible-near infrared (400-1100 nm) sensor for the monitoring of fat and fatty acids content in milk during the manufacturing process of milk. The optical, mechanical and electronic designs of the sensor have been developed in Tekniker IK4 research centre just as its manufacturing process. The measurement range of the sensor is 400-1100 nm thus it covers the visible range (400-780 nm) and the short-wave near infrared (780-1100 nm). Chemometric techniques were applied with the purpose of obtaining a predictive model for each parameter correlating the spectra obtained by the sensor with the parameters analysed in the laboratory. The models were developed by Partial Least Squares Regression (PLS) obtaining one model for each parameter. The raw milk samples used in this work were provided by CAPSA (Asturias, Spain).
Sensors
In this work we present a surface plasmon resonance sensor based on enhanced optical transmission... more In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices.
Analytica Chimica Acta, 2011
This paper describes the calibration process of a Visible-Near Infrared sensor for the condition ... more This paper describes the calibration process of a Visible-Near Infrared sensor for the condition monitoring of a gas engine's lubricating oil correlating transmittance oil spectra with the degradation of a gas engine's oil via a regression model. Chemometric techniques were applied to determine different parameters: Base Number (BN), Acid Number (AN), insolubles in pentane and viscosity at 40 • C. A Visible-Near Infrared (400-1100 nm) sensor developed in Tekniker research center was used to obtain the spectra of artificial and real gas engine oils. In order to improve sensor's data, different preprocessing methods such as smoothing by Saviztky-Golay, moving average with Multivariate Scatter Correction or Standard Normal Variate to eliminate the scatter effect were applied. A combination of these preprocessing methods was applied to each parameter. The regression models were developed by Partial Least Squares Regression (PLSR). In the end, it was shown that only some models were valid, fulfilling a set of quality requirements. The paper shows which models achieved the established validation requirements and which preprocessing methods perform better. A discussion follows regarding the potential improvement in the robustness of the models.
Laser Sources and Applications, 2012
Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used ... more Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used in different industrial applications sectors such as automobile, microfluidic, electronic and biomedicine. This technique offers several advantages over conventional methods, especially when a local deposition of energy and minimum thermal distortions are required. In LTW one of the polymeric materials needs to be transparent to the laser wavelength and the second part needs to be designed to be absorbed in IR spectrum. This report presents a study of laser weldability of ABS (acrylonitrile/butadiene/styrene) filled with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). These additives are used as infrared absorbing components in the laser welding process, affecting the thermal and optical properties of the material and, hence, the final quality of the weld seam. A tailored laser system has been designed to obtain high quality weld seams with widths between 0.4 and 1.0mm. It consists of two diode laser bars (50W per bar) coupled into an optical fiber using a non-imaging solution: equalization of the beam quality factor (M 2) in the slow and fast axes by a pair of micro step-mirrors. The beam quality factor has been analyzed at different laser powers with the aim to guarantee a coupling efficiency to the multimode optical fiber. The power scaling is carried out by means of multiplexing polarization technique. The analysis of energy balance and beam quality is performed in two linked steps: first by means ray tracing simulations (ZEMAX ®) and second, by validation. Quality of the weld seams is analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. The optimum laser power range for three different welding speeds is determinate meanwhile the clamping pressure is held constant. Additionally, the corresponding mechanical shear tests were carried out to analyze the mechanical properties of the weld seams. This work provides a detailed study concerning the effect of the material microstructure and laser beam quality on the final weld formation and surface integrity.
Agente: No consta 54 Título: Método de predicción lineal óptima para la reconstrucción de la imag... more Agente: No consta 54 Título: Método de predicción lineal óptima para la reconstrucción de la imagen en cámaras digitales con sensor de mosaico. Aviso: Se puede realizar consulta prevista por el art. 37.3.8 LP.
Electro-Optical and Infrared Systems: Technology and Applications, 2004
Despite MTF is widely accepted as the most complete figure of merit describing optical quality of... more Despite MTF is widely accepted as the most complete figure of merit describing optical quality of image intensifier tubes(IIs), it is not well-established neither in industrial nor governmental testing laboratories. This work aims to advance in the standardization of MTF testing procedures for modern IIs. A versatile device to measure MTF of IIs, based on different FFT related methods, was
Optical Sensing and Detection, 2010
ABSTRACT Marine engine oils are used for years without an oil change. During this long period of ... more ABSTRACT Marine engine oils are used for years without an oil change. During this long period of time the oil gets contaminated, not only by water and fuel but also by solid contaminants due to oxidation of the base oil, overreacted additives soot and other products of Heavy Fuel Oil combustion. This paper shows the design, development and assembly of a visible-near infrared (400-1100 nm) sensor that monitors several characteristics corresponding to in-use marine engine oil condition. Also, chemometric techniques (PLS) are applied for determining TBN, %insoluble in pentane, soot and water from visible-near infrared spectra, having in mind the low resolution capability of the extracted on-line sensor signal. Different prediction models for each oil parameter were obtained. These prediction models were developed by partial least squares regression from the VIS/NIR spectra. Finally, the sensor has been tested at low-speed crosshead engine (two stroke engine). So that, reference values for TBN, %insoluble in pentane, soot and water were obtained in the laboratory for every sample. During the validation test, the models showed: a) a correlation higher than or equal to 0.85; b) the slope for the regression model tends to one; c) low bias; and d) the root mean square error of prediction (RMSEP) and the standard error of performance (SEP) were similar and close to the laboratory's estimated error.
Optical Sensing and Detection, 2010
The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and indust... more The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with
IEEE International Conference on Image Processing 2005, 2005
We present an efficient Linear Minimum Mean Square Error (LMMSE) method for reconstructing full c... more We present an efficient Linear Minimum Mean Square Error (LMMSE) method for reconstructing full color images from single sensor Color Filter Array (CFA) data. We use a representative set of full color images to estimate the joint spatial-chromatic covariance among pixel color components. Then, we derive from it a set of joint color-space, small linear kernels which predict the missing color samples as linear combinations of their neighbor observed samples. The color arrangement of the local mosaic varies with the window's location, and this results into a different predictor for every local mosaic and color sample. As an extension, we include blur and noise in the training process, obtaining localized mosaic-constrained Wiener estimators that partially compensate for these degradations. We show that this simple method provides an excellent trade-off between performance and computational cost.
Electro-Optical and Infrared Systems: Technology and Applications II, 2005
The most straightforward way to describe the performance of an image intensifier tube, especially... more The most straightforward way to describe the performance of an image intensifier tube, especially under adverse conditions, is to predict the image it yields. In this work we have developed two different methods to provide realistic simulated images in low light level conditions: 1) Approximate Physical Model. A classical approach based on the simulation of the different degradation sources. It provides a good understanding of the image formation process. 2) Synthesis-by-analysis of real images. The observed noise is modelled through texture analysis tools and the image blur through the MTF. The resulting simulated images for both methods were compared with real intensified images (laboratory chart sights and natural images) taken under controlled conditions, close to the performance limits of an image intensifier tube. Both methods generated good results in terms of visual comparison for different object sizes, contrasts or luminances. These methods can be used as a new tool to predict the performance thresholds of the image intensifier. Only well-known or measurable parameters were used as input for the methods.
Electro-Optical Remote Sensing, 2005
In this paper, a decision support system for ship identification is presented. The system receive... more In this paper, a decision support system for ship identification is presented. The system receives as input a silhouette of the vessel to be identified, previously extracted from a side view of the object. This view could have been acquired with imaging sensors operating at different spectral ranges (CCD, FLIR, image intensifier). The input silhouette is preprocessed and compared to those stored in a database, retrieving a small number of potential matches ranked by their similarity to the target silhouette. This set of potential matches is presented to the system operator, who makes the final ship identification. This system makes use of an evolved version of the Curvature Scale Space (CSS) representation. In the proposed approach, it is curvature extrema, instead of zero crossings, that are tracked during silhouette evolution, hence improving robustness and enabling to cope successfully with cases where the standard CCS representation is found to be unstable. Also, the use of local curvature was replaced with the more robust concept of lobe concavity, with significant additional gains in performance. Experimental results on actual operational imagery prove the excellent performance and robustness of the developed method.
Procedia Engineering, 2012
ABSTRACT
Optik - International Journal for Light and Electron Optics, 2014
An efficient flat-top illuminating optical system optimized for an extended light source is prese... more An efficient flat-top illuminating optical system optimized for an extended light source is presented. The source is a high-brightness high divergence light emitting diode (LED), sized 1 mm × 1 mm, producing monochromatic emission (525 ± 5 nm) with viewing angle of 130 •. The design is based on a rotationally symmetrical catadioptric system, developed on a geometrical optics basis, and modelled with ZEMAX ® software. The device consists of two optical systems: (i) a collimating system which, in turn, is formed by an aspheric lenses system (low numerical apertures, NA < 0.26) and two-mirror system (0.26 < NA < 0.86), and (ii) an external mirror (NA > 0.86) designed and optimized for each purpose. By itself, the collimating system works with a residual divergence of  C = 1.46 •. The external mirror can be adequately designed to produce some given conditions. For instance, a flat-top profile is obtained in the selected focusing plane, with a maximum transversal intensity variation of 2.5% over 18 mm. In addition, when the focusing mirror is allowed to move along the optical axis in a ±1 mm range, other interesting profiles can be reached for a given working distance, therefore increasing the versatility of the system.
Optical Engineering, 2012
Laser transmission welding (LTW) of thermoplastics is a direct bonding technique already used in ... more Laser transmission welding (LTW) of thermoplastics is a direct bonding technique already used in different industrial applications sectors such as automobiles, microfluidics, electronics, and biomedicine. LTW evolves localized heating at the interface of two pieces of plastic to be joined. One of the plastic pieces needs to be optically transparent to the laser radiation whereas the other part has to be absorbent, being that the radiation produced by high power diode lasers is a good alternative for this process. As consequence, a tailored laser system has been designed and developed to obtain high quality weld seams with weld widths between 0.7 and 1.4 mm. The developed laser system consists of two diode laser bars (50 W per bar) coupled into an optical fiber using a nonimaging solution: equalization of the beam parameter product (BPP) in the slow and fast axes by a pair of step-mirrors. The power scaling was carried out by means of a multiplexing polarization technique. The analysis of energy balance and beam quality was performed considering ray tracing simulation (ZEMAX®) and experimental validation. The welding experiments were conducted on acrylonitrile/butadiene/styrene (ABS), a thermoplastic frequently used in automotive, electronics and aircraft applications, doped with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). Quality of the weld seams on ABS was analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. Mechanical properties of weld seams were analyzed by mechanical shear tests. High quality weld seams were produced in ABS, revealing the potential of the laser developed in this work for a wide range of plastic welding applications.
Microelectronic Engineering, 2014
In the present work thermal nanoimprint lithography of various commercial thermoplastic resists a... more In the present work thermal nanoimprint lithography of various commercial thermoplastic resists as matrixes for perylenediimides (PDIs) has been studied. This fabrication method reduced the number of fabrication steps, and therefore, the cost of the obtained distributed feedback (DFB) lasers. The optical properties of these devices are analyzed, aiming to optimize their performance.
Journal of Applied Physics, 2012
We report on the preparation and characterization, under optical pump, of second-order onedimensi... more We report on the preparation and characterization, under optical pump, of second-order onedimensional distributed feedback (DFB) lasers based on polystyrene films doped with a perylenediimide derivative, as active media. The DFB gratings were engraved on the substrates (SiO 2) by thermal nanoimprint lithography, followed by reactive ion etching. Laser emission wavelength was tuned from 554 to 583 nm by changing film thickness (h) between 240 and 1200 nm. The effect on the performance (emission wavelength, threshold, slope efficiency, number of modes, and spectral shape) of varying the grating depth (d) from 30 to 240 nm, for the whole range of h values, has been investigated. Although there is extensive work in the literature aiming to tune the emission wavelength of organic DFB lasers by h variation, the effect of changing d systematically has not been previously studied. Experimental results have been interpreted by models that take into account the presence of the grating by averaging either h or the effective refractive index. Single-mode emission (k 0) was observed for h < 1000 nm, while for thicker films lasing appeared at two different wavelengths (k 0 and k 1). Models indicate that k 0 and k 1 correspond to the TE 0 and TE 1 waveguide modes, respectively. It was found that d plays an important role in determining the DFB thresholds and slope efficiencies for two h regimes: (i) For h < 350 nm, lowest thresholds and highest slopes efficiencies were obtained with the shallower gratings; and (ii) for h > 1000 nm, d affects significantly the losses associated with the TE 1 mode, so single mode emission was achieved at k 0 or at k 1 for deep and shallow gratings, respectively. Finally, the shape of the emission spectra, both below and above threshold, has also been analyzed in order to clarify the physical mechanisms responsible for the existence of gain. Bragg dips were observed in the spectra below threshold only for devices with d/h larger than around 0.3 and their width increased with increasing d/h. In these cases, single-mode DFB emission appeared at the long-wavelength edge of the Bragg dip, indicating that index-coupling modulation contributes significantly to the gain process. On the other hand, for smaller d/h values, Bragg dips became too small to be detected, so gain coupling becomes the dominant mechanism accounting for the presence of gain.
Food Chemistry, 2012
This paper describes the calibration, validation and testing process of a low-cost on-line visibl... more This paper describes the calibration, validation and testing process of a low-cost on-line visible-near infrared (400-1100 nm) sensor for the monitoring of fat and fatty acids content in milk during the manufacturing process of milk. The optical, mechanical and electronic designs of the sensor have been developed in Tekniker IK4 research centre just as its manufacturing process. The measurement range of the sensor is 400-1100 nm thus it covers the visible range (400-780 nm) and the short-wave near infrared (780-1100 nm). Chemometric techniques were applied with the purpose of obtaining a predictive model for each parameter correlating the spectra obtained by the sensor with the parameters analysed in the laboratory. The models were developed by Partial Least Squares Regression (PLS) obtaining one model for each parameter. The raw milk samples used in this work were provided by CAPSA (Asturias, Spain).
Sensors
In this work we present a surface plasmon resonance sensor based on enhanced optical transmission... more In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices.